Plan for healthy harbour
DELWYN DICKEY
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HALTING the decline of Mahurangi Harbour has become a passion for many people living along its shoreline.
While still in relative good health, Auckland Regional Council environmental monitoring has shown the harbour is in decline.
Sediment from steep clay hills has been smothering marine life, such as cockles, on the harbour floor. Large numbers of shellfish and other organisms are important to the harbour's health for filter feeding and cleaning the water.
Mangroves are also able to establish more easily around the harbour edges with silt build-up.
Five years ago, the Mahurangi Action Plan was set up as a pilot project with the Auckland Regional Council, the Rodney District Council, community groups and other interested people – many living around the harbour and its tributaries.
The aim was to monitor the harbour and come up with new land management practices which would reduce sediment entering it, says ARC sustainable catchments programme leader Kim Morresey.
Research by the National Institute of Water and Atmospheric Research showed the silt was coming mostly from cattle close to waterways and tree felling operations disturbing the soil.
Since 2004, initiatives included research into pastoral farming practices to reduce silt runoff, as well as pilot farm plans which outline environmental protection and restoration processes for land owners without compromising economic returns.
About 43km of riparian fencing now protects 200ha from stock access. More than 55,000 native species have been planted by volunteers putting in nearly 9000 hours, and 1000 local people are involved with the scheme – with the ARC contributing $950,000 over the past three years in funding.
Now the Mahurangi Action Plan has been extended to the year 2030.
Broader issues such as water quality, access, land use and landscapes are under study, and more input from locals and groups is sought.
Like many farmers around the harbour, dry stock farmers Mike and Norma Neil are behind the plan.
When they bought their 50ha hilly farm 18 years ago the fences, typical of many in the area, ran straight down to the harbour edges. Their cattle would often wander out on to the flats at low tide and eat the mangroves.
Wanting to leave the land better than they found it saw them fence off the shoreline and bush soon after arriving, as well as putting in sediment trap dams. Over the years the fencing has reduced the sediment entering the harbour from their property.
They put up their own money for planting on their property, including 1500 kauri and pohutukawa trees. Last year they received funding from several sources, including from the Rodney District Council's natural heritage fund, for another 1200 trees, plus another contribution from the ARC for 1000.
They applied for funding this year under the plan to remove pine trees from land bordering Mahurangi West Rd to open up views of the harbour and to construct a public viewing platform.
Sediment flushing into the Mahurangi River has raised the level of the river bed.
Access up the river to Warkworth is now believed to be significantly reduced from when sailing ships regularly visited the town. Home to the flat-bottomed scow the Jane Gifford, the boat has only two hours either side of high tide to operate, says Peter Thompson of Warkworth.
"The Warkworth wharf was completed 10 years ago," he says. "Since then the silt level has risen two metres up the piles."
For information on the Mahurangi Action Plan see www.arc.govt.nz/environment/coastal-and-marine/mahurangi-action-plan.
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